iss) had «ad toed) had 0d hed Ok Cd qu" , » a fo ¥. — ' bem ah Table 1. Number of soil sample locations on each island (continued). No. of Sample Locations Surface (0-15 cm) Eneu North of airstrip South of airstrip TOTAL Profiles (0-90 cm) 60 40 350 2 2 12 (6 samples each) The exact soil sampling locations will actually be determined by a random selection process to obtain statistically meaningful and unbiased results. Special samples will also be collected within "hot spot" areas or other areas of specialized interest. The samples will be placed in plastic bags with appropriate identification tags and readied for ship- ment to LLL, where they will undergo preprocessing and gamma-spectral analysis. It is anticipated that analyses for other radionuclides of interest, such as plutonium-239 and strontium-90, will be performed at a contractor laboratory. Purpose: Gamma-Exposure Rate Survey The gamma-ray exposure measurements program conducted on the ground is designed to provide detailed examination of the geographical variability of the exposure rates on Bikini and Eneu Islands, and to provide overall verification of exposure rate measurements made during previous visits. Methods and Measurements The program utilizes the Baird-Atomic scintillation detector which consists of a 2.5-cm-diam x 3.9-cm-long NaI crystal with ratemeter readout. The instrument is calibrated with a !3’Cs point source on the primary calibration range of the National Environmental Research Center, Las Vegas, Nevada. While the response of this instrument is energy-dependent, our experience at Enewetak showed that this was not a serious limitation because of the dominance of !3’Cs in the radiation background on the Atoll. We will also utilize the Reuter-Stokes high pressure ionization chamber. The current produced by the radiation induced ionization within the chamber is measured by a sensititive electrometer with digital readout. The instrument exhibits a flat energy response over all gamma-ray energies of interest to this survey. It is capable of measuring exposure rates from about 1 uR/hr to 200 yR/hr with an accuracy of about 5%. Thus, the results derived from this instrument may be chosen as a reference to which measurments obtained by’ other techniques can be compared. 4 ¥ yA